TankBud

Hornwort

Ceratophyllum demersum

Also known as Coontail, Rigid hornwort

FreshwaterBrackishStemCuttingsSide shoots

Hornwort (Ceratophyllum demersum)
Totodilefan · Public domain

Care at a glance

Light
Low light
CO2
No CO₂ needed
Temperature
59–86°F
15–30°C
Max height
39.4 in
100 cm
Growth rate
Fast
Placement
Floating
Type
Stem
pH
6.0–7.5
Hardness
5–15 dGH
Spread
5.9 in (15 cm)
Nutrient uptake
Water column
Growth region
Submersed
Difficulty
Beginner
Family
Ceratophyllaceae
Origin
Cosmopolitan (native to all continents except Antarctica)

Overview

Hornwort is a fast-growing stem plant, usually floated, and about as forgiving as aquarium plants get. It is a beginner plant for freshwater or brackish tanks.

Did you know

Hornwort is allelopathic. It releases compounds into the water that suppress algae and even slow down competing plants. That is part of why a healthy clump keeps a tank so clear.

Caring for hornwort

Float hornwort, wedge a bundle behind decor, or weigh a stem down with a plant weight. It needs no substrate.

Low light is enough, and it needs no CO2. It feeds entirely from the water column, so a liquid fertilizer is the way to feed it. That makes it excellent at soaking up ammonia and nitrate, and a go-to for cycling tanks and shrimp setups. It handles 59 to 86°F (15 to 30°C).

It grows fast and can reach about 39 in (100 cm), so thin it out often. To propagate it, snip or pinch off a side shoot and let it grow.

Expect needle-drop now and then. After a move or a parameter swing it can shed leaves and leave bare stems. It usually pushes new growth from the tips within a week or two.

Good to know

Hornwort belongs to the sole surviving genus of the family Ceratophyllaceae, an ancient lineage near the very base of the flowering plants. It has no roots at all. The genus name comes from the Greek for horn and leaf. It refers to the stiff, forked, antler-like whorls of leaves that crowd toward the stem tips. Hornwort is also sold as coontail.

In the wild

Hornwort lives in still and slow-moving fresh water on every continent except Antarctica, from ponds and lakes to ditches and slow rivers. It grows fully submersed, drifting in the water column or loosely anchored in soft sediment by pale modified leaves.

Common questions

Does hornwort need to be planted in the substrate?

No. Hornwort can drift at the surface or be anchored in the substrate. It takes its nutrients from the water either way.

Does hornwort need CO2?

No. Hornwort grows well without added CO2 and suits a low-tech tank.

How much light does hornwort need?

Hornwort is a low-light plant, and the light that comes with a standard tank kit is enough for it.

How do you propagate hornwort?

Hornwort propagates by cuttings and side shoots. Any length of stem cut off grows into a new plant. Cut a side shoot off once it has a few leaves and plant it on its own.

How tall does hornwort grow?

Hornwort grows to about 39.4 in (100 cm) tall. It grows fast, so expect to trim or thin it out often.

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